1. Field of the Invention
The present invention relates to a booster, and more particularly to a booster of a fuel cell.
2. Description of the Prior Art
Energy plays an essential role in our lives. With the improvement and progress of technology, different power-supply equipment has been invented for different sorts of electrical products. The design and quality of power-supply systems may directly influence the quality of electrical systems. A stable power supply allows electrical equipment to work in a stable condition, and also allows better performance with less noise. On the other hand, if the power supply is unstable, unexpected operation or circuit malfunction can occur. Therefore, increasingly higher quality of today's electrical products is needed, so that producing good and stable power supplies has become an important issue.
A fuel cell is a kind of environmental energy source. However, fuel cells can only provide lower electrical power than the operation power of normal electrical products. Furthermore, a fuel cell outputs different voltage because of different external electrical equipment connected to the fuel cell. For solving this problem, a transformer is added external to the fuel cell for adjusting the output voltage of the fuel cell to a predetermined voltage value to provide a fixed and high-stability power supply to different sorts of electrical products.
Please refer to FIG. 1, which is a diagram of a booster 10 external to a battery 12 according to the prior art. The booster 10 comprises a boosting circuit 11, a battery 12, and a feedback oscillation controller 14. The boosting circuit 11 is electrically connected to the battery 12 and used for adjusting the voltage of the battery 12 to a predetermined voltage value. The feedback oscillation controller 14 detects the output voltage of the boosting circuit 11 and utilizes the output voltage as a feedback signal to change the period of the oscillating signal generated by the feedback oscillation controller 14 for controlling the boosting circuit 11.
Tank devices, such as capacitors and inductances, are often set up inside the boosting circuit 11. These tank devices need a periodic signal or an AC signal to store or transform energy. The oscillating signal generated by the feedback oscillation controller 14 is therefore provided to the boosting circuit 11 for boosting.
The theory behind the function of the feedback oscillation controller 14 is to utilize an oscillating signal of pulse width modulation to control the boosting circuit 11. If the output voltage added by the booster does not reach a predetermined value, the feedback oscillation controller 14 outputs an oscillating signal with a longer period to make boosting faster. Similarly, if the output voltage added by the booster has reached the predetermined value, the feedback oscillation controller 14 outputs an oscillating signal with a shorter period to make the boosting slower.
However, even when the output voltage of the prior art booster has reached the predetermined value, the feed-back oscillation controller 14 still continuously outputs oscillating signals. But in fact, at this time, the boosting circuit 11 does not need the oscillating signals because the mechanism of boosting can be paused. As a result of the continuous oscillating signals outputted by the feed-back oscillation controller 14, the following disadvantages could occur. First, power is lost unnecessarily when there is no need for boosting. And second, because of the power consumption inside the booster, the battery can only provide lower power to the external loads. As a result, there is a need for a booster that can stop the function of charging when the output voltage reaches the predetermined value to solve the prior art problems.